1. Field of the Invention
This invention relates generally to computer networking, and more particularly to network stack layer interfaces for efficiently communicating data between network stack layers in a computer network environment.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform Chemical Mechanical Polishing (CMP) operations, including polishing, buffing and wafer cleaning. Typically, integrated circuit devices are in the form of multi-level structures. At the substrate level, transistor devices having diffusion regions are formed. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define the desired functional device. As is well known, patterned conductive layers are insulated from other conductive layers by dielectric materials, such as silicon dioxide. As more metallization levels and associated dielectric layers are formed, the need to planarize the dielectric material increases. Without planarization, fabrication of additional metallization layers becomes substantially more difficult due to the higher variations in the surface topography. In other applications, metallization line patterns are formed in the dielectric material, and then metal CMP operations are performed to remove excess metallization.
In the prior art, CMP systems typically implement belt, orbital, or brush stations in which belts, pads, or brushes are used to scrub, buff, and polish one or both sides of a wafer. Slurry is used to facilitate and enhance the CMP operation. Slurry is most usually introduced onto a moving preparation surface, e.g., belt, pad, brush, and the like, and distributed over the preparation surface as well as the surface of the semiconductor wafer being buffed, polished, or otherwise prepared by the CMP process. The distribution is generally accomplished by a combination of the movement of the preparation surface, the movement of the semiconductor wafer and the friction created between the semiconductor wafer and the preparation surface.
FIG. 1 illustrates an exemplary prior art CMP system 10. The CMP system 10 in FIG. 1 is a belt-type system, so designated because the preparation surface is an endless belt 18 mounted on two drums 24 which drive the belt 18 in a rotational motion as indicated by belt rotation directional arrows 26. A wafer 12 is mounted on a carrier 14. The carrier 14 is rotated in direction 16. The rotating wafer 12 is then applied against the rotating belt 18 with a force F to accomplish a CMP process. Some CMP processes require significant force F to be applied. A platen 22 is provided to stabilize the belt 18 and to provide a solid surface onto which to apply the wafer 12. Slurry 28 composing of an aqueous solution such as NH4OH or DI containing dispersed abrasive particles is introduced upstream of the wafer 12. The process of scrubbing, buffing and polishing of the surface of the wafer is achieved by using an endless polishing pad glued to belt 18. Typically, the polishing pad is composed of porous or fibrous materials and lacks fix abrasives.
After the polishing pad polishes a limited number of wafers, the surface of the pad is conditioned or xe2x80x9cdressedxe2x80x9d in order to return the pad surface to the surface""s original state. Subsequent conditioning, the polishing pad will generally have a significant amount of glazing, causing the polishing pad to lose effectiveness. The polishing pad also loses its effectiveness due to normal wear of the material itself. As a result, the polishing pad must be replaced in its entirety.
The removal of the used polishing pad and its subsequent replacement with a new polishing pad is very time consuming and labor intensive. Additionally, the time needed to perform the replacement necessarily requires that the polishing system be taken off-line, which thus reduces throughput.
To reduce the time needed to perform the pad replacement, efforts have been made to introduce a single-piece polymer belt into the CMP system. However, problems arise when using a single-piece polymer belt due to stretching of the belt, which causes the belt tension to change and introduces variability into the CMP process. Moreover, belt steering and endpoint detection window alignment problems occur for similar reasons.
In view of the foregoing, a need exists for a chemical mechanical polishing system that will enable use of a polishing pad that is less expensive to maintain and is more effectively serviced after its use degrades the effectiveness of the polishing. Moreover, the system should reduce belt steering and endpoint detection window alignment problems.
Broadly speaking, the present invention fills these needs by providing an interlocking CMP belt system. The interlocking CMP belt system of the present invention uses a single-piece polymer belt pad, thus greatly reducing the time needed for belt pad replacement. Further, interlocking CMP belt of the present invention greatly reduces belt steering and endpoint detection window alignment problems related to single-piece polymer belts.
In one embodiment, an interlocking polishing belt apparatus is disclosed. The interlocking polishing belt apparatus includes an interlocking belt, which includes a plurality of studs, each having an upper stud end and a lower stud end. In addition, the interlocking polishing belt apparatus includes a polishing belt that is in contact with the interlocking belt. The polishing belt has a plurality of polishing belt stud holes, each configured to interlock with an upper stud end.
In another embodiment, a method for performing chemical mechanical polishing utilizing an interlocking polishing belt is disclosed. Initially, an interlocking belt is provided that includes a plurality of studs, each having an upper stud end and a lower stud end. A polishing belt is then attached to the interlocking belt. The polishing belt includes a plurality of polishing belt stud holes each configured to interlock with an upper stud end.
An interlocking polishing belt system is disclosed in a further embodiment of the present invention. The interlocking polishing belt system includes at least one drum having a plurality of stud receiving holes. It should be noted that the system may actually include any number of drums, often two drums are used. The interlocking polishing belt system also includes an interlocking belt having a plurality of studs, each having an upper stud end and a lower stud end. The lower stud end of each stud is capable of being inserted into a stud receiving hole of the drum. Further, a polishing belt having an outer surface and an inner surface is included in the system. The polishing belt is in contact with the interlocking belt, and includes a plurality of polishing belt stud holes disposed within the inner surface. Each of the polishing belt stud holes is capable of interlocking with an upper stud end. Finally, a carrier capable of applying a wafer to the outer surface of the polishing belt is included in the system.
Advantageously, embodiments of the present invention allow the use a single-piece polishing pad belt, thus reducing the time needed for pad replacement. Further, embodiments of the present invention greatly reduce belt steering a endpoint detection window alignment problems. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.